The invention relates to a dialysis process for purifying the blood by exchange across the peritoneal membrane during a continuous peritoneal process.
Heretofore, artificial kidney users have relied basically on two processes for purifying the blood. Hemodialysis involves the circulation of blood through a dialysis machine in which an exchange of toxic metabolites takes place across an artificial membrane outside the patient's body. This process requires the assistance of trained personnel and subjects the patient to dangers of mechanical malfunction, and rapid shifts of fluid and metabolites, and surgery involving blood vessels, is involved.
Peritoneal dialysis involves the installation of a sterile dialysate into the peritoneal cavity. The dialysate is discarded after absorbing waste metabolites. The process is repeated until the blood level of metabolites is reduced to a desired level. This method is commonly referred to as the "Batch" method due to the fact that numerous one or two liter bottles or bags of fresh dialysate solution are utilized, requiring multiple connections to be made to the catheter inserted in the peritoneal cavity. The multiple connections made during the course of the dialysis have been thought to be a major cause of the high instance of peritonitis.
Chronic ambulatory peritoneal dialysis offers peritoneal dialysis while still allowing the patient freedom of movement. However, the chronic ambulatory peritoneal dialysis must be done in absence of a machine. Multiple bottles or bags of dialysis must be infused daily. The bag of dialysate is worn by the patient. The multiple installations per day require that multiple connections of bags or bottles to the peritoneal catheter be made. The production of bulk sterile dialysis for the peritoneal process has not been shown to be practical for large scale application particularly for home dialysis.
U.S. Pat. No. 4,311,587 seeks to avoid some of the above problems with peritoneal dialysis by providing a sub-micron filter on line with the fresh dialysate to prevent peritoneal contamination. The system is perambulatory and the bag of dialysate is worn by the patient. The bag may be pressurized by numerous methods and is connected only to the inflow side of the filter. The outflow port of the filter is connected on the other side of the filter so that no peritoneal contaminating source is connected directly to the peritoneal cavity. The system is still basically a batch type system in that multiple bottles or bags of dialysate must be connected to the filter even though direct connection to the peritoneal catheter is not required.
U.S. Patent No. 4,338,190 discloses a system and process which attempts to avoid the batch process method utilized heretofore in peritoneal dialysis wherein a closed loop peritoneal circuit is provided having a selective membrane across which toxic metabolites are exchanged. A solution is passed on the other side of the selective membrane to maintain the original concentration of sugar and salt in the peritoneal fluid as the toxic metabolites pass the separator membrane. A concentrate of sugar and salts is mixed at a desired ratio with water to make up the dialysis fluid. The conductivity of the fluid may be automatically monitored to adjust the concentration of the fluid during its recirculation. A double peritoneal catheter provides for the inflow and outflow of the peritoneal fluid. The peritoneal fluid is constantly recirculated through the peritoneal cavity. The efficiency of the dialysis becomes reduced slightly because of residual toxins which are put back into the peritoneal cavity. The selective membrane is an expensive disposable item which means that the cost of operating the system is high unless the membrane is recleaned. Pumping the peritoneal fluid through the peritoneal cavity is required making it difficult to assure that the patient stays properly distended during the dialysis process. If the peritoneal membrane is not fully distended, it becomes convoluted around the intestines and pockets are formed where the peritoneal fluid can sequester. Incomplete circulation results in decreased efficiency of dialysis. No control is maintained over the level of peritoneal fluid in the peritoneal circuit. There is no way of replenishing the peritoneal fluid should the circuit run low on fluid or run dry.
U.S. Pat. No. 3,545,438 discloses a peritoneal dialysis method which provides for partially reusing a portion of the dialysis fluid. The spent fluid becomes mixed with fresh dialysate. There is no control or monitoring of the fluid in and out as would allow the dialysate to flow in the peritoneal cavity in a continuous manner.
U.S. Patent No. 3,707,967, corresponding to German Patent No. 2,149,040, apparently discloses a closed loop dialysis system wherein the dialysis fluid is continuously circulated through the peritoneal membrane, generally without flow control and monitoring of inflow and outflow lines in a continuous manner.
U.S. Pat. No. 3,709,222 discloses a peritoneal dialysis method generally of the batch type. The amount of dialysis fluid entering the peritoneal cavity and the pressure of the peritoneal cavity are controlled by varying the height of a pressure relief chamber. This can be both inaccurate and unreliable, and requires that an attendant be present in order to carry out the process. The cycles involved in the process are rather complicated involving an initial priming cycle which involves the filling of a proportion chamber, the pressure relief chamber and a return chamber. To begin the process, dialysis fluid is allowed to enter the peritoneal cavity from the pressure relief chamber until the chamber is moved to a lower position which prevents the fluid from flowing. Next, an automatic cycling begins in which the fluid is pumped out of the cavity into the return chamber. Next, an inflow cycle begins in which the fluid is pumped from the return chamber to the proportional chamber which forces fresh dialysis from the proportioning chamber into the pressure relief chamber from where it flows into the patient. Next, there is an equilibrium cycle in which dialysis fluid is drained from the proportioning chamber and fresh dialysis fluid is added. Apparently, during this time, dialysis fluid remains in the cavity. The process then switches back to the outflow cycle in which fluid is pumped from the cavity to the return chamber.
French Patent No. 2,371,931 discloses a peritoneal process having a single line used for inflow and outflow. The method includes pumping in a certain amount of dialysate, letting it equilibrate for a prescribed dwell time, and removing the dialysate. This is, in essence, an automatic "batch" system.
U.S. Pat. No. 4,412,917 discloses a peritoneal dialysis system wherein a prescribed volume of fluid is pumped into the peritoneal cavity and drained. The installation of fluid to the patient can be controlled by counting pump revolutions or pumping time and by monitoring the total weight of the reservoirs which contain the source and drain fluids to achieve a desired amount of fluid received by the patient. After the fluid is drained, the patient's fluid balance is determined by weighing the increase and total weight of fluid on output scales to indicate the extra amount of fluid (ultrafiltrate) received from a patient. The fill and drain cycles may be repeated until either a desired amount of fluid is used or the change in fluid balance reported by the scales is of a desired magnitude.
It is also known in peritoneal dialysis to use a reverse osmosis unit to supply water which is passed through a heat exchanger for heating. The water is subsequently mixed with a dialysis concentrate, and optionally, dextrose, which are mixed in a predetermined ratio to provide a dialysate. The dialysate may be gravity fed or pumped to the patient, and thereafter drained either by gravity or pumping in a semiautomatic manner. However, the system is complex for the patient to operate, and has difficulty in meeting safety requirements. It is also known to mix dextrose with the water and dialysis concentrate to effect the osmolality over pressure sensors are utilized to sense an excessive pressure condition in the peritoneal cavity.
Tidal peritoneal dialysis is a technique where, after an initial fill of the peritoneal cavity, less than 50% of dialysate is drained and replaced by fresh dialysis fluid with each cycle, leaving the majority of the dialysate in constant contact with the peritoneal membrane until the end of the dialysis session when the fluid is drained as completely as possible. The factors determining the efficiency of dialysis with the tidal technique include the minimum volume of fluid in the peritoneal cavity assuring constant and full contact between the peritoneal membrane and dialysate, that is the reserve volume, and proper mixing of fluid in the peritoneal cavity by a sufficiently high tidal exchange volume. While the technique of tidal peritoneal dialysis is sound and efficient, there is a lack of suitable systems for implementing the tidal technique of peritoneal dialysis in a practical manner. None of the prior peritoneal dialysis methods and systems described previously are entirely suitable.
Accordingly, an important object of the present invention is to provide a continuous peritoneal dialysis system and method which avoid the inherent problems and dangers of a batch type peritoneal dialysis system.
Still another important object of the present invention is to provide a peritoneal dialysis system having a high rate of dialysate exchange providing increased dialysis efficiency.
Still another important object of the present invention is to provide a peritoneal dialysis system and method having a high rate of dialysate exchange and dialysis efficiency in which the osmolality of the fluid is continuously adjusted in response to the amount of fluid removed from the patient.
Still another important object of the present invention is to provide a continuous peritoneal dialysis system and method which may be used to carry out a continuous peritoneal dialysis using tidal dialysis techniques in the patient's peritoneal membrane.
Yet another important object of the present invention is to provide a continuous flow peritoneal dialysis system and method in which the pressure and volume of dialysate in the patient's peritoneal membrane may be monitored without the need of a medical attendant.